1. Field of the Invention
The present invention relates to a method for forming fine pitch contacts and fine pitch contacts obtained thereby. Particularly, the present invention relates to a method for forming fine pitch contacts used in a Zero Insertion Force (ZIF) socket and fine pitch contacts used in a ZIF socket.
2. Description of Prior Art
As shown in FIGS. 4 and 5, a conventional contact 9 used in a ZIF socket is illustrated. The conventional contact 9 comprises a soldering portion 93 configured as a round plate for being surface-mounted on a printed circuit board through a solder ball attached thereon, a retaining portion 92 extending vertically with respect to the soldering portion 93 and connected thereto through a connecting tab 95, and a contacting portion 91 for electrically engaging with a pin of a Central Processing Unit (CPU) mounted on the ZIF socket for establishing an electrical connection between the CPU and the printed circuit board. The contacting portion 91 has a neck portion 914 connecting with the retaining portion 92 and a pair of resilient arms 910 projecting oppositely from the neck portion 914 and between which a circular receiving space 913 is defined for receiving the pin of the CPU. The pair of resilient arms 910 have a pair of cantilever contacting fingers 912 defining an engaging gap 911 therebetween.
The conventional contact 9 as described above is formed by the following steps:
a. providing a contact strip with a plurality of contacts stamped thereon (only one stamped contact 9xe2x80x2 shown in FIG. 5);
b. curving the horizontal portions 91xe2x80x2 of the stamped contact 9xe2x80x2 to form the resilient arms 910 defining a circular receiving space 913 therebetween and the contacting fingers 912 confronting each other;
c. bending the round portion 93xe2x80x2 of the stamped contact 9xe2x80x2 to be vertical to the joint portion 92xe2x80x2 to respectively form the soldering portion 93 and the retaining portion 92 of the final contact 9; and
d. inserting the plurality of stamped contacts 9xe2x80x2 in a housing of the ZIF socket and cutting the plurality of stamped contacts 9xe2x80x2 from the contact strip to obtain the final contacts 9.
To maintain a fine pitch (which is 1.27 mm as well known in the art) between two adjacent contacts in the ZIF socket, the width xe2x80x9cAxe2x80x9d of the expanded contacting portion 91xe2x80x2 stamped on the contact strip should at least double the pitch, that is, at least 2.54 mm. Thus, a problem of the above method for forming the conventional contact is that the expanded contact 9xe2x80x2 shown in FIG. 5 wastes a great deal of material.
Furthermore, residual stress is accumulated in the contacting portion 91 when curving the resilient arms 910 of the contacting portion 91 by a bending device.Once the contacting portions 91 of the contacts 9 are removed from the bending device, the pairs of resilient arms 910 will deviate from their intended positions due to stress relaxation. When this happens, the contacting portions 91 of the contacts 9 are unable to accurately mate with the pins of the CPU, thereby adversely affecting a proper engagement between the CPU and the printed circuit board.
Hence, an improved method for forming a contact used in a ZIF socket is required to overcome the above-mentioned disadvantages of the prior art.
A first object of the present invention is to provide a method for forming fine pitch contacts used in a ZIF socket and fine pitch contacts obtained thereby, whereby the space occupied by contacts stamped on a contact strip can be greatly decreased to thus reduce the manufacturing cost of the contacts.
A second object of the present invention is to provide a method for forming fine pitch contacts used in a ZIF socket and fine pitch contacts obtained thereby, whereby the deviation problem of contacting portions of the contacts from their intended positions due to stress relaxation can be effectively solved.
To fulfill the above-mentioned objects, a method for forming fine pitch contacts used in a ZIF socket in accordance with the present invention comprises the following steps:
a. stamping a contact strip comprising a carrier strip and a plurality of contacts, each contact comprising a first portion opposite the carrier strip, a retaining portion extending from the first portion to the carrier strip, and a second portion projecting from the retaining portion and connecting with the carrier strip, the first portion, the retaining portion and the second portion being coplanar with each other, the first portion comprising a pair of arcuate arms defining a circular receiving space therebetween and a pair of parallel contacting fingers extending from respective distal ends of the pair of arcuate arms;
b. bending the first portions of the contacts to form contacting portions perpendicular to the retaining portions and the second portions;
c. bending the second portions of the contacts to form soldering portions perpendicular to the retaining portions and parallel to the contacting portions; and
d. inserting the plurality of contacts in a housing of the ZIF socket and cutting them from the carrier strip.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.